1. Field of the Invention
The present invention relates generally to an improved magnetic head suspension assembly (HSA) and more specifically to a low profile mechanical connection mechanism or assembly for connecting a pair of head suspension assemblies to an actuator arm.
2. Description of the Prior Art
Magnetic head suspension assemblies are used in magnetic disc storage devices or disc drives for the purpose of positioning and supporting a read/write transducer head or slider at one end relative to a rotating disc. A common construction is to have a plurality of such rotating discs which are spaced relative to one another about a common rotational axis. In a multiple disc system, a pair of oppositely disposed head suspension assemblies are positioned between the discs, with one HSA of each pair associated with respective opposing sides of the adjacent discs. The end of the head suspension assembly opposite the slider is connected to a rigid actuator arm. The memory density or memory capacity for a given space and given track density for a multiple disc system is determined principally by the distance between the spaced discs. The closer the discs are spaced, the greater the memory density. Accordingly, there is and has been a need for reducing the disc spacing to thereby result in increased memory capacity.
Currently, a pair of head suspension assemblies are attached to a rigid actuator arm through the use of base plates positioned on opposite sides of the arm. These base plates and the load beams to which they are welded or otherwise connected, are part of the suspension assemblies and are either screwed or swaged to the support arm. In prior art screw connections, small screws extend through holes in the base plates and arm and are retained on the opposite side by a threaded tap in the arm or by a threaded nut plate as disclosed in U.S. Pat. No. 4,912,583 issued to Hinlein on Mar. 27, 1990.
In prior art swage connections, the base plates each include an opening and a generally cylindrical projection or boss designed for extension into a corresponding hole in the actuator arm. A prior art swage connection is disclosed in U.S. Pat. No. 4,829,395 issued to Coon on May 9, 1989. In these prior swage connections, the thickness of the actuator arm must be sufficient to accommodate the bosses of both base plates. Following initial assembly, a steel swaging ball or other means is forced through the openings in the respective bosses thereby deforming the same and causing an interference fit between the outer cylindrical surface of the bosses and the inner cylindrical surface of the opening in the actuator arm. Because of a certain, predetermined minimum length requirements of each of the bosses, the amount that the thickness of the support arm can be reduced is limited. Prior art screw connections have similar actuator arm thickness requirements. Because of these requirements, the amount which the distance between the discs can be reduced is limited. Thus, the memory density of the unit is similarly limited.
Alternative methods of achieving minimum disc spacing, less than that provided by screw or conventional swage connections, are by bonding, welding or otherwise permanently securing the head suspension assemblies directly to the actuator arm. Although this will permit further reduction of the width of the actuator arm, these methods generally require expensive processes and induce a large loss when rework is needed. In the event of a suspension assembly failure, the entire actuator arm must be discarded or a costly HSA removal process must be utilized.
Accordingly, there is a need for an improved head suspension assembly and more particularly, an improved, low profile connection mechanism or assembly by which a pair of head suspension assemblies can be connected to an actuator arm in a manner which reduces or minimizes the thickness of the actuator arm, but which still permits individual HSA's or pairs of HSA's to be easily and inexpensively removed from the actuator arm and replaced.